Diastereoselektive Synthese voncis- odertrans-2,3-substituierten Tetrahydrofuranen und 3,4-substituierten 4-Butanoliden

Lewis Acid-Catalyzed Vinyl Acetal Rearrangement of 4,5-Dihydro-1,3-dioxepines: Stereoselective Synthesis of cis- and trans-2,3-Disubstituted Tetrahydrofurans

Lewis acid-catalyzed rearrangements of 4,5-dihydro-1,3-dioxepines have been investigated. Rearrangement of vinyl acetals under a variety of conditions resulted in cis- and trans-2,3-disubstituted tetrahydrofuran derivatives in a highly stereoselective manner. Rearrangements at lower temperatures typically provided the cis-2,3-disubstituted tetrahydrofuran carbaldehydes. At higher temperatures, the corresponding trans-2,3-disubstituted tetrahydrofuran carbaldehydes are formed. The requisite substrates for the vinyl acetal rearrangement were synthesized via ring-closing olefin metathesis of bis(allyoxy)methyl derivatives using Grubbs second-generation catalyst followed by olefin isomerization using a catalytic amount of RuCl₂(PPh₃)₃. We examined the substrate scope using substituted aromatic and aliphatic derivatives. Additionally, the rearrangement was utilized in the synthesis of a stereochemically-defined bis-tetrahydrofuran (bis-THF) derivative, which is one of the key structural elements of darunavir, an FDA-approved drug for the treatment of HIV/AIDS.

Lewis Acid-Catalyzed Additions of (Benzotriazol-1-yl)diethoxymethane to Enol Ethers and Enamides. New Syntheses of beta-Alkoxyalkanal and beta-Aminoalkanal Acetals

Addition of (benzotriazol-1-yl)diethoxymethane 11 to various acyclic and cyclic enol ethers and enamides produces the corresponding adducts, which were reacted with either NaAlH(4) or Grignard reagents to afford acyclic acetal-ethers (18a-f), cyclic alpha-(substituted)-beta-acetals (19a-c), amino-acetals (24a,b), and 1,3-amino-ethers (25), all known but previously difficult-to-access classes of compounds.